During and after the drilling of bore holes, as, for example, in the oil and gas industry, core samples are utilized to obtain accurate information relative to formations containing resources of interest. Such samples are commonly taken at the bottom of a bore hole prior to continuing the boring process through a formation of interest.
It is also very advantageous to be able to obtain substantial core samples at various levels in a hole, after the hole has been drilled and logged. After drilling, examination of open hole logs and bore hole cuttings can identify levels from which such additional core samples would be useful.
There are currently a number of methods available for obtaining samples from formations at various levels in an open hole. All such currently available methods have serious shortcomings. For example, in many cases only very small diameter cores can be obtained. In other methods multiple trips into and out of the hole are required for each sample With many methods the cores are short and/or do not represent the lithology changes along the bore hole.
The present invention is directed toward a method and apparatus for obtaining a core sample of sufficient length and diameter from the formation generally along the axis of bore hole, at a selected level in an existing bore hole and requires only a single trip into the hole.